DE102011009260B4 - Determination of the rotation parameters of the eyes - Google Patents

Abstract

Method for determining movement parameters for at least one eye of a user with the following steps:- generating first image data of at least a partial area of the eye in a first viewing direction of the eye;- generating second image data of at least a partial area of the eye in a second viewing direction different from the first Line of sight of the eye, the first and second image data being generated with an image recording device, which is fixed relative to the user's head to generate the first and second image data in such a way that it assumes the same position relative to the user's head to generate the first and second image data ,- determining a change in position of at least one marked point of the eye; and- determining a movement radius of the at least one marked point of the eye from the determined change in position and as a function of the first and second viewing direction.

Description

The present invention relates to a method, a device and a computer program product for the individual determination of movement parameters for at least one eye of a spectacle wearer. In particular, the invention relates to an individual determination of movement parameters, which requires only a single image recording device and can therefore be integrated in many, in particular compact, aberrometers or other optical devices.

U.S. 2009/0109400 A1 describes a method with which a viewing direction is determined from an image based on a head and eye model. First of all, the orientation of the head, i.e. the face, is determined in the horizontal and vertical direction. For this purpose, the position of individual facial organs (e.g. eyebrows, eyes, nose, mouth) within the depicted boundaries of the head is evaluated using automatic image recognition. Under the model assumption of a given ellipticity of the head, their decentralized positioning results in the horizontal and vertical angle of the orientation of the face. Based on the measurements of the direction of the face, an evaluation is then made of the position of the pupil of an eye relative to the entire visible area of the eye in order to determine the direction of gaze.

U.S. 2010/0013949 A1 describes a technique for automatically detecting a person's line of sight, for example. For this purpose, a procedure is described, among other things, with which in an iterative approximation method from an image of a face based on a model of the face, among other things, an eye center and an eye radius are determined as eye parameters in such a way that a point in space viewed by the eye, a pupil center and the center of the eye lies at least approximately on a straight line.

In addition to other parameters, the pupil distance when looking into the distance (distance PD) is currently measured to adjust glasses. A measurement of the actual pupillary distances for viewing objects in the near or intermediate range only takes place in exceptional cases and is often not very precise and error-prone. For an even more precise adjustment of the spectacle lenses to the wearer, the position of the center of rotation of the eye is taken into account, both for lenses available on the market and for lenses currently being developed by Rodenstock.

The object of the present invention is to achieve an improvement in the individual adjustment of spectacle lenses, in particular when looking for different object distances and different eye positions. In particular, it is an aim of the invention to make this improvement as simple and compact as possible to implement. This object is achieved by a method having the features specified in claim 1, a device having the features specified in claim 13 and a computer program product having the features specified in claim 15. Preferred embodiments are subject of the dependent claims.

• - Erzeugen von ersten Bilddaten zumindest eines Teilbereichs des Auges, welcher insbesondere zumindest einen ausgezeichneten Punkt des Auges umfasst, bei einer ersten Blickrichtung des Auges;
• - Erzeugen von zweiten Bilddaten zumindest eines Teilbereichs des Auges, welcher insbesondere den zumindest einen ausgezeichneten Punkt des Auges umfasst, bei einer von der ersten Blickrichtung verschiedenen zweiten Blickrichtung des Auges, wobei die ersten und zweiten Bilddaten mit einer Bildaufnahmeeinrichtung (z.B. einer Kamera) erzeugt werden, welche zum Erzeugen der ersten und zweiten Bilddaten derart relativ zum Kopf des Benutzers visiert wird, dass zum Erzeugen der ersten und zweiten Bilddaten dieselbe Position (also dieselbe Aufnahmerichtung und denselben Abstand) relativ zum Kopf des Benutzers einnimmt. Die ersten und zweiten Bilddaten werden zu verschiedenen Zeitpunkten bzw. in verschiedenen Zeitintervallen, also nacheinander erzeugt.

The invention thus offers a method for determining movement parameters for at least one eye of a user with the following steps:

• - generation of first image data of at least a partial region of the eye, which in particular comprises at least one marked point of the eye, in a first viewing direction of the eye;
• - Generation of second image data of at least a partial area of the eye, which in particular includes the at least one marked point of the eye, in a second viewing direction of the eye that differs from the first viewing direction, the first and second image data being generated with an image recording device (e.g. a camera). , which is sighted relative to the user's head to generate the first and second image data in such a way that the same position (ie the same recording direction and the same distance) relative to the user's head occupies the same position for generating the first and second image data. The first and second image data are generated at different points in time or at different time intervals, ie one after the other.

In addition, the method according to the invention includes determining a change in position of the at least one marked point of the eye; and a determination of a movement radius of the at least one marked point of the eye from the determined change in position and as a function of the first and second viewing direction, in particular as a function of a first and a second angular deflection of the first and second viewing direction relative to an optical axis of the image recording device .

It is therefore sufficient to provide a single image recording device (eg camera) with which at least two image data sets are generated one after the other, which are also referred to here as first and second image data. Care is only taken to ensure that the user's head is in the same position for both image recordings occupies relative to the imaging device. In addition to the at least two image data sets, one or a large number of further image data sets could also be generated. In particular, an entire video sequence could be generated. In this case, it is preferably ensured that the user's head remains unchanged relative to the image recording device during the recording of these image data sets or the video sequence, while a change in the viewing direction is definitely desirable and possibly even motivated. As will be explained in more detail later, the statistical measurement uncertainty can be significantly improved by including more than two image data, and parameters of more complex models can also be determined as a result. Such more complex models preferably include different movement radii of the at least one marked point of the eye for different directions of the eye movement. A first radius of movement for a horizontal gaze movement is preferably determined as the radius of movement. In addition, a second radius of movement for a vertical gaze movement is preferably determined.

The invention presented here makes it possible to determine rotation parameters of an eye by determining excellent properties of the eye (such as the position and size of the pupil or other objects in the front eye, as well as the orientation of the eye) and, as a rotation parameter, a movement radius of an excellent point of the eye to determine.

A decisive advantage compared to conventional methods is the ability to be integrated into an aberrometer, so that a system can be provided with which both the optical (aberrometric measurements) and the mechanical properties of an eye can be measured. A particular advantage of the procedure according to the invention is that many elements that are used in any case in aberrometers can also be used to measure the rotation parameters. As a result, the system can be designed in a compact and cost-effective manner. Furthermore, mature technology can be used for corresponding subsystems. It is also advantageous that the measurement of the rotation parameters is independent of the principle used for measuring the optical parameters. The system can thus be combined with all aberrometers - regardless of whether they use methods according to (Shack-)Hartmann, Moiree, Tschering or Scheiner. This means that it can also be integrated into other (ophthalmic) devices such as autorefractometers, kerato- and topographers.

The first and second image data are preferably generated by means of a telecentric image recording device, i.e. the image recording device preferably has telecentric optics. The distances between recorded image elements of the eye that are depicted in the image data are therefore independent of the distance between the image recording device and the eye, which ensures a very precise and reliable determination of position and possibly angle changes.

The at least one marked point preferably comprises the center of the pupil and/or the center of the iris and/or the corneal vertex of the eye. Alternatively or additionally, the at least one marked point comprises an optically significant point of the iris and/or the sclera. These can be found, for example, using the known methods of pattern matching. To determine the center points mentioned, the corresponding edges (e.g. via edge detection) can be found within the framework of image processing and the center points can be derived geometrically from these edges. Alternatively, a focus formation of the pupils or iris surfaces can be used.

While knowledge of the lateral position of the center of rotation of the eye (or the vertex of the cornea or the center of the pupil) is essentially used for centering (lateral position of the lens in the fitted frame), knowing the axial positions of the center of rotation of the eye, the vertex of the cornea (or the center of the pupil) and Spectacle lens the glass can be further optimized in the position of use. Essentially, the distances, ie the radius of movement of the corneal vertex (or the center of the pupil) and the distance between the corneal vertex (or the center of the pupil) and the spectacle lens are relevant.

1. 1. Geometrische Lage der Durchblickspunkte Die genaue laterale Position der Durchblickspunkte für verschiedene Blickrichtungen durch ein Brillenglas hängt neben der lateralen Position des Durchblickspunktes in Nullblickrichtung („klassische Zentrierung“) auch von den genannten Parametern ab. Durch deren Kenntnis kann die Position des Durchblickspunktes für jeden gegebenen Vergenzwinkel - und damit für jede gegebene Objektentfernung - sowie für jeden vertikalen Blickwinkel bestimmt werden. Dies erlaubt beispielsweise den genauen Verlauf (horizontal und vertikal) der Hauptblicklinie in Gleitsichtgläsern und die Position des Einsatzes für die Addition individuell zu optimieren
2. 2. Durchblicksrichtung Abhängig von den genannten Größen ändert sich weiterhin die Richtung, durch die das einfallende Strahlenbündel eines abzubildenden Objekts auf eine bestimmte Position des Brillenglases auftrifft. Durch die Ermittlung der genauen Einfallsrichtung aus den genannten Größen (und gegebenenfalls der Grundgeometrie des Glases) lassen sich die Abbildungseigenschaften verbessern und dabei insbesondere der Astigmatismus schiefer Bündel minimieren.
3. 3. Vergrößerung Da der Abstand zwischen verschiedenen optischen Elementen zueinander einen Einfluss auf die resultierende Vergrößerung hat, kann durch die genaue Kenntnis der genannten Größen die tatsächliche Vergrößerung bei der Optimierung berücksichtigt und das Brillenglas entsprechend optimiert werden. So kann beispielsweise vermieden werden, dass die resultierende Vergrößerung von der Entfernung oder der lateralen Position des abzubildenden Objekts abhängt.

In detail, the following aspects depend on the variables mentioned:

1. 1. Geometric position of the visual points The exact lateral position of the visual points for different viewing directions through a lens depends not only on the lateral position of the visual point in the zero visual direction (“classic centering”) but also on the parameters mentioned. By knowing this, the position of the visual point can be determined for any given vergence angle - and thus for any given object distance - as well as for any vertical viewing angle. This allows, for example, the exact course (horizontal and vertical) of the main line of sight in progressive lenses and the position of the insert for the addition to be individually optimized
2. 2. Direction of viewing Depending on the variables mentioned, the direction through which the incident beam of rays of an object to be imaged impinges on a specific position of the spectacle lens also changes. Determining the exact direction of incidence from the variables mentioned (and possibly the basic geometry of the glass) can improve the imaging properties and, in particular, minimize the astigmatism of oblique beams.
3. 3. Magnification Since the distance between different optical elements has an influence on the resulting magnification, the actual magnification can be taken into account in the optimization process and the spectacle lens can be optimized accordingly if the precise knowledge of the stated values is known. For example, it can be avoided that the resulting magnification depends on the distance or the lateral position of the object to be imaged.

• Dabei wird insbesondere durch ein erfindungsgemäßes Verfahren der Radius der Bewegung des Hornhautscheitels (bzw. der Pupillenmitte) bestimmt. Aus Messungen mit einem Videozentriersystem (vorzugsweise mit einem Stereokameraystem vom Typ ImpressionIST) können die axiale und laterale Position des Hornhautscheitels (bzw. der Pupillenmitte) beim Blick in Nullblickrichtung (sowie ggf. weiterer Blickrichtungen) und die Position des Glases bestimmt werden. Daraus lassen sich dann die laterale und axiale Position des Augendrehpunktes sowie der Abstand des Brillenglases vom Homhautscheitel (bzw. der Pupillenmitte) bestimmen.

The set of parameters mentioned (lateral and axial position of the center of rotation of the eye, radius of movement of the corneal vertex (or the center of the pupil) and distance of the spectacle lens from the corneal vertex (or the center of the pupil)) is preferably determined in the following way:

• In this case, the radius of the movement of the corneal vertex (or the center of the pupil) is determined in particular by a method according to the invention. Measurements with a video centering system (preferably with an ImpressionIST stereo camera system) can be used to determine the axial and lateral position of the corneal vertex (or the center of the pupil) when looking in the zero viewing direction (and possibly other viewing directions) and the position of the lens. From this, the lateral and axial position of the center of rotation of the eye and the distance of the spectacle lens from the corneal vertex (or the center of the pupil) can be determined.

The first and second viewing direction preferably lie in a common plane with an optical axis of the image recording device, with the first or the second viewing direction particularly preferably being parallel to the optical axis of the image recording device.

The method preferably includes specifying the first and/or second viewing direction by means of a fixation target, which is designed to emit a light field at least partially in the direction of the user's eye to be recorded by means of the image recording device in such a way that all light rays within the light field are essentially parallel to a common plane of fixation, wherein the light field is emitted during the generation of the first image data with a first plane of fixation and during the generation of the second image data with a second plane of fixation different from the first.

Alternatively or additionally, the method preferably includes specifying the first and/or second line of sight by means of a fixation object, which is designed to output an optical signal suitable for guiding or fixing the line of sight of the user in at least one specified fixation position.

The method preferably includes determining a change in angle between the first and second viewing directions of the eye, with the radius of movement of the at least one marked point of the eye being determined from the determined change in position and the determined change in angle. The determination of a change in angle particularly preferably includes determining the angle between the first and second specified viewing direction and/or determining a first angle (first angular deflection) between the first viewing direction and an optical axis of the image recording device and a second angle (second angular deflection) between the second viewing direction of the optical axis of the image recording device.

Alternatively or additionally, a change in angle or angles (angular deflections) for viewing directions that are not specified by a fixation target or a fixation object are determined by means of the perspective projection of elements of the eye (e.g. the pupil or the iris) in the image data. However, it is not absolutely necessary for the change in angle or the angles to be explicitly determined and/or output. Rather, the perspective projection is preferably used as a measure for the viewing angle or its change directly for determining the radius of movement, ie it is taken into account.

• - ein Bestimmen eines ersten primären, projizierten (also sichtbaren bzw. abgebildeten) Durchmessers der Pupille und/oder der Iris des Auges in einer Primärrichtung aus den ersten Bilddaten; und
• - ein Bestimmen eines zweiten primären, projizierten (also sichtbaren bzw. abgebildeten) Durchmessers der Pupille und/oder Iris des Auges in der Primärrichtung aus den zweiten Bilddaten.

Preferably, the method includes:

• - a determination of a first primary, projected (ie visible or imaged) diameter of the pupil and/or the iris of the eye in a primary direction from the first image data; and
• - a determination of a second primary, projected (ie visible or imaged) diameter of the pupil and/or iris of the eye in the primary direction from the second image data.

The radius of movement of the at least one marked point of the eye is particularly preferably determined from the determined change in position and at least the ratio of the first and second primary, projected diameter.

In particular in this context, the center of the pupil and/or the center of the iris is preferably used as a distinguished point. These can be determined particularly easily as the center point of the pupil diameter (or iris diameter) determined in each case. In particular, the first and second viewing directions preferably lie in a common plane with the primary direction. The optical axis of the image recording device also particularly preferably lies in the same plane. When examining the movement parameters, in particular the determined radius of movement, for horizontal gaze movements of the eye, the primary direction is therefore in the horizontal. This allows the perspective distortion of the horizontal diameter to be used to automatically determine the viewing directions.

mit dem ersten primären, projizierten Durchmesser d'₁ und dem zweiten primären, projizierten Durchmessers d'₂ bestimmt wird. Dies ist besonders vorteilhaft, wenn die erste Blickrichtung parallel zur optischen Achse der Bildaufnahmeeinrichtung (Kameraachse) liegt. In diesem Fall kann davon ausgegangen werden, dass der abgebildete Durchmesser bei der ersten Blickrichtung unverzerrt ist, während der aus den zweiten Bilddaten erfasste Durchmesser eine der Winkeländerung bzw. Winkelauslenkung, insbesondere der zweiten Winkelauslenkung, entsprechende perspektivische Verzerrung erfährt. Dabei wird angenommen, dass der tatsächliche Durchmesser der Pupille bzw. Iris sich während der beiden Aufnahmen nicht ändert, was insbesondere für die Iris in sehr guter Näherung sogar unabhängig von den Lichtverhältnissen erfüllt ist. Um diese Näherung auch für die Pupille zu einem möglichst genauen Ergebnis zu führen, wird vorzugsweise während beider Aufnahmen die dem Auge zugeführte Lichtmenge konstant gehalten.The first image data is particularly preferably generated in a first viewing direction of the eye, which is parallel to an optical axis of the image recording device,
wherein a change in position Δa' ₁₂ of a center point of the pupil and/or a center point of the iris is detected as a change in position of the at least one marked point, and
where the radius of movement r of the center of the pupil or the center of the iris according to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2}{\mathrm{i.e}{\text{'}}_1}\right)}^2}},$

with the first primary projected diameter d' ₁ and the second primary projected diameter d' ₂ is determined. This is particularly advantageous if the first viewing direction is parallel to the optical axis of the image recording device (camera axis). In this case, it can be assumed that the diameter shown is undistorted in the first viewing direction, while the diameter recorded from the second image data undergoes a perspective distortion corresponding to the angular change or angular deflection, in particular the second angular deflection. It is assumed here that the actual diameter of the pupil or iris does not change during the two recordings, which is fulfilled in a very good approximation, in particular for the iris, even independently of the lighting conditions. In order to lead this approximation to a result that is as accurate as possible for the pupil as well, the amount of light supplied to the eye is preferably kept constant during both recordings.

• - ein Bestimmen eines ersten sekundären, projizierten (also sichtbaren bzw. abgebildeten) Durchmessers h₁ der Pupille bzw. der Iris des Auges in einer insbesondere zur Primärrichtung senkrechten Sekundärrichtung aus den ersten Bilddaten; und
• - ein Bestimmen eines zweiten sekundären, projizierten also sichtbaren bzw. abgebildeten Durchmessers h₂ der Pupille bzw. der Iris des Auges in der Sekundärrichtung aus den zweiten Bilddaten.

Alternatively or additionally, the method preferably also comprises:

• - a determination of a first secondary, projected (ie visible or imaged) diameter h ₁ of the pupil or the iris of the eye in a secondary direction, in particular perpendicular to the primary direction, from the first image data; and
• - a determination of a second secondary, ie projected visible or imaged diameter h ₂ of the pupil or the iris of the eye in the secondary direction from the second image data.

und $\frac{d{\text{'}}_2}{h_2}$

des jeweils primären d'₁ bzw. d'₂ zum sekundären h₁ bzw. h₂, projizierten Durchmesser bestimmt.The radius of movement of the at least one marked point of the eye from the determined change in position and the conditions is particularly preferred $\frac{\mathrm{i.e}{\text{'}}_1}{{\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="DE102011009260B4\_0047.png,DE102011009260B4\_0051.png"\; state="\{\{state\}\}">H</figure-callout>}}_1}$

and $\frac{\mathrm{i.e}{\text{'}}_2}{{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="DE102011009260B4\_0047.png"\; state="\{\{state\}\}">H</figure-callout>}}_2}$

of the respective primary d' ₁ or d' ₂ to the secondary h ₁ or h ₂ , projected diameter.

The secondary direction is particularly preferably perpendicular to a common plane of the optical axis and the at least two viewing directions. The secondary, projected diameter preferably corresponds to the actual diameter of the pupil in the secondary direction, i.e. the image of the diameter in this direction is not reduced by the projection onto the image plane of the recording device. In this way, a variable diameter can also be taken into account during the two recordings, it being assumed that the ratio of the two diameters does not change. For example, this is fulfilled with a very good approximation even for a variable pupil size due to changing light conditions.

bestimmt wird. Dies ist besonders
vorteilhaft, wenn die erste Blickrichtung parallel zur optischen Achse der Bildaufnahmeeinrichtung (Kameraachse) liegt. Dabei kann sogar für einen elliptischen Außenumfang der Pupille oder Iris eine geeignete Auswertung erfolgen.The first image data is particularly preferably generated in a first viewing direction of the eye, which is parallel to an optical axis of the image recording device,
wherein a change in position Δa' ₁₂ of the center of the pupil or of the center of the iris is detected as the change in position of the at least one marked point, and
where the radius of movement r of the center of the pupil or the center of the iris according to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2\cdot H_1}{\mathrm{i.e}{\text{'}}_1\cdot H_2}\right)}^2}},$

is determined. This is special
advantageous if the first viewing direction is parallel to the optical axis of the image recording device (camera axis). A suitable evaluation can even be carried out for an elliptical outer circumference of the pupil or iris.

bestimmt
wird. Dies ist besonders vorteilhaft, wenn von einem kreisförmigen Außenumfang der Pupille bzw. Iris ausgegangen wird. Damit ist sogar eine Auswertung möglich, wenn keine der beiden Blickrichtungen parallel zur Kameraachse liegt und sogar für eine variable Größe der Pupille. Das Vorzeichen wird dabei je nach Sehaufgabe gewählt. Für zwei Auslenkungen der Blickrichtung, die in Bezug auf die Kameraachse entgegengesetzt sind, werden die Beträge der Wurzel addiert, während sie für zwei Auslenkungen in die gleiche Richtung relativ zur Kameraachse subtrahiert werden.A change in position Δa' ₁₂ of the center of the pupil or the center of the iris is preferably recorded as the change in position of the at least one marked point, with the radius of movement r of the center of the pupil or of the center of the iris corresponding to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2}{H_2}\right)}^2}\pm \sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_1}{H_1}\right)}^2}}$

definitely
will. This is particularly advantageous if a circular outer circumference of the pupil or iris is assumed. This means that an evaluation is even possible if neither of the two viewing directions is parallel to the camera axis and even for a variable size of the pupil. The sign is selected depending on the visual task. For two deflections of the viewing direction that are opposite with respect to the camera axis, the magnitudes of the square root are added, while for two deflections in the same direction relative to the camera axis, they are subtracted.

Preferably, the method includes illuminating the eye with a reference light source, wherein capturing the first image data includes capturing a first position of the first Purkinje reflex of the eye and a first position of the fourth Purkinje reflex of the eye, and capturing the second image data detecting a second position of the first Purkinje reflex of the eye and a second position of the fourth Purkinje reflex of the eye, and wherein the change in position of the at least one marked point of the eye and/or the change in angle between the first and second viewing direction of the eye or the first and/or second angular deflection in the first or second viewing direction of the eye can be determined as a function of the first and second positions of the first and fourth Purkinje reflex. The reference light source particularly preferably emits infrared light. A comparatively high light intensity can thus be used without dazzling the user. This is particularly advantageous in order to still be able to capture the fourth Purkinje reflex well, the intensity of which is significantly lower than the intensity of the first Purkinje reflex. The first Purkinje reflex results from a reflection of the reference light on the front surface of the cornea of the eye, while the fourth Purkinje reflex results from a reflection of the reference light on the rear surface of the lens of the eye. The change in position of the at least one marked point of the eye and the change in angle between the first and second viewing direction of the eye or the first and/or second angular deflection in the first or second viewing direction of the eye are determined using Purkinje transformations.

mit der Positionsänderung Δp⁽¹⁾ des ersten Purkinje-Reflexes und einem vorgegebenen Wert h⁽¹⁾ bestimmt.The method preferably includes determining a change in angle between the first and second viewing directions by determining a change in position Δp ⁽¹⁾ of the first Purkinje reflex and determining the change in angle according to Δα ₁₂ =h ⁽¹⁾ Δp ⁽¹⁾ with a predetermined constant value h ⁽¹⁾ , which is also called the Hirschberg quotient of the first Purkinje reflex. In particular, a value h ⁽¹⁾ in the range from approximately 10°/mm to approximately 16°/mm, preferably in the range from approximately 11°/mm to approximately 14°/mm, could be specified for this. The value h ⁽¹⁾ is preferably specified in accordance with statements in the publication by F. Schäffel “Binocular Lens Tilt and Decentration Measurements in Healthy Subjects with Phakic Eyes”, Investigative Ophthalmology & Visual Science, 49 (5), 2216-2222 (2008). . This procedure is particularly preferred if the angular deflection relative to the optical axis of the image recording device is known for at least one viewing direction, in particular if the first or second viewing direction coincides with the optical axis of the image recording device or is parallel thereto. In this case, a change in position Δa' ₁₂ of a center point of the pupil and/or a center point of the iris is particularly preferably detected as a change in position of the at least one marked point, and the movement radius r of the center point of the pupil or the center point of the iris according to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(H^{\left(1\right)}\cdot \mathrm{\Delta }{p}^{\left(1\right)}\right)},$

with the change in position Δp ⁽¹⁾ of the first Purkinje reflex and a predetermined value h ⁽¹⁾ .

des Abstandes $d_i^{\left(\mathrm{1,4}\right)}=p_i^{\left(1\right)}-p_i^{\left(4\right)}$

zwischen einer Position $p_i^{\left(1\right)}$

des ersten Purkinje-Reflexes und einer Position $p_i^{\left(4\right)}$

des vierten Purkinje-Reflexes jeweils bei der i-ten Blickrichtung bestimmen. Dabei wird davon ausgegangen, dass der Abstand $d_i^{\left(\mathrm{1,4}\right)}$

zwischen dem ersten und vierten Purkinje-Reflex gemäß α = h^(1,4) · d^(1,4) ein Maß für den Blickwinkel ist, wobei h^(1,4) als Parameter vorgegeben wird. Vorzugsweise wird der Parameter h^(1,4) mit einem Wert im Bereich von etwa 5°/mm bis etwa 8°/mm, vorzugsweise mit einem Wert von etwa $h^{\left(\mathrm{1,4}\right)}=\frac{1}{2}\cdot h^{\left(1\right)}$

mit dem oben beschriebenen Hirschbergquotienten h⁽¹⁾ für den ersten Purkinje-Reflex vorgegeben.In a further preferred embodiment, using the first and the fourth Purkinje reflex, in particular according to a presentation in TN Cornsweet, et al. "Accurate two-dimensional eye tracker using first and fourth Purkinje images", J. Opt. Soc. Am., 63 (8), 921-928 (1973) determined an angular deflection and a translational deflection of the eye from the distance between the two reflexes or the position of the geometric center of both reflexes. A change in the angle between the first and second viewing direction can thus be achieved particularly preferably by determining a change $\begin{array}{l}\mathrm{\Delta }{\mathrm{i.e}}_{12}^{\left(1.4\right)}={\mathrm{i.e}}_2^{\left(1.4\right)}-{\mathrm{i.e}}_1^{\left(1.4\right)}\\ {\mathrm{i.e}}_i^{\left(1.4\right)}=p_i^{\left(1\right)}-p_i^{\left(4\right)}\\ H^{\left(1.4\right)}=\frac{1}{2}\cdot H^{\left(1\right)}\end{array}$

the distance ${\mathrm{i.e}}_i^{\left(1.4\right)}=p_i^{\left(1\right)}-p_i^{\left(4\right)}$

between a position $p_i^{\left(1\right)}$

of the first Purkinje reflex and a position $p_i^{\left(4\right)}$

of the fourth Purkinje reflex in the i-th viewing direction. It is assumed that the distance ${\mathrm{i.e}}_i^{\left(1.4\right)}$

between the first and fourth Purkinje reflex according to α = h ^(1,4) d ^(1.4) is a measure of the viewing angle, with h ^(1.4) given as a parameter. Preferably, the parameter h is set to ^(1.4) with a value in the range from about 5°/mm to about 8°/mm, preferably with a value of about $H^{\left(1.4\right)}=\frac{1}{2}\cdot H^{\left(1\right)}$

with the Hirschberg quotient h ⁽¹⁾ described above for the first Purkinje reflex.

in Abhängigkeit von einer Änderung $\mathrm{\Delta }{p}_{12}^{\left(1\right)}=p_2^{\left(1\right)}-p_1^{\left(1\right)}$

der Position des ersten Purkinje-Reflexes und einer Änderung $\mathrm{\Delta }{p}_{12}^{\left(4\right)}=p_2^{\left(4\right)}-p_1^{\left(4\right)}$

der Position des vierten Purkinje-Reflexes ermittelt, wobei ƒ als Parameter vorgegeben wird. Vorzugsweise wird der Parameter ƒ mit einem Wert von 1 vorgegeben (ƒ=1mm/mm).A _change in accordance with $\mathrm{\Delta }{a}_{12}=ƒ\cdot \frac{\left(\mathrm{\Delta }{p}_{12}^{\left(1\right)}+\mathrm{\Delta }{p}_{12}^{\left(4\right)}\right)}{2}$

depending on a change $\mathrm{\Delta }{p}_{12}^{\left(1\right)}=p_2^{\left(1\right)}-p_1^{\left(1\right)}$

the position of the first Purkinje reflex and a change $\mathrm{\Delta }{p}_{12}^{\left(4\right)}=p_2^{\left(4\right)}-p_1^{\left(4\right)}$

determined from the position of the fourth Purkinje reflex, where ƒ is specified as a parameter. The parameter ƒ is preferably specified with a value of 1 (ƒ=1mm/mm).

• - eine Bilddatenaufnahmeeinrichtung, welche ausgelegt ist zum Erzeugen von ersten Bilddaten zumindest eines Teilbereiches des Auges bei einer ersten Blickrichtung des Auges und zum Erzeugen von zweiten Bilddaten zumindest eines Teilbereichs des Auges bei einer zweiten Blickrichtung des Auges, wobei die Bilddatenaufnahmeeinrichtung derart relativ zum Kopf des Benutzers fixierbar ist, dass sie zum Erzeugen der ersten und zweiten Bilddaten dieselbe Position relativ zum Kopf des Benutzers einnimmt; und
• - eine Auswerteeinrichtung, welche ausgelegt ist zum
  • -- Ermitteln einer Positionsänderung zumindest eines ausgezeichneten Punktes des Auges; und
  • -- Bestimmen eines Bewegungsradius des zumindest einen ausgezeichneten Punktes des Auges aus der ermittelten Positionsänderung und in Abhängigkeit von der ersten und zweiten Blickrichtung, insbesondere in Abhängigkeit von der einer ersten und einer zweiten Winkelauslenkung der ersten bzw. zweiten Blickrichtung relativ zu einer optischen Achse der Bildaufnahmeeinrichtung.

In a further aspect, the invention offers a device for determining movement parameters for at least one eye of a user, comprising:

• - an image data recording device, which is designed to generate first image data of at least a partial area of the eye in a first viewing direction of the eye and to generate second image data of at least a partial area of the eye in a second viewing direction of the eye, the image data recording device being relative to the user's head in this way is fixable to occupy the same position relative to the user's head for generating the first and second image data; and
• - An evaluation device, which is designed for
  • -- determining a change in position of at least one marked point of the eye; and
  • -- Determining a radius of movement of the at least one marked point of the eye from the determined change in position and as a function of the first and second viewing direction, in particular as a function of a first and a second angular deflection of the first and second viewing direction relative to an optical axis of the image recording device .

The device preferably comprises at least one fixation target, which is designed to at least partially define the first and/or second line of sight by emitting a light field in that all light rays of the light field run essentially parallel to a common fixation plane. The device is particularly preferably designed to carry out one of the methods described here automatically, at least in part.

In addition to corresponding methods for determining movement parameters for at least one eye of a user, in particular including one or more of the corresponding method steps implemented as functional processes in the systems according to the invention, the invention also offers a computer program product, in particular in the form of a storage medium or a signal sequence, comprising computer-readable instructions, which, when loaded into a memory of a computer and executed by the computer, cause the computer to perform a method according to the present invention, particularly in a preferred embodiment. The invention thus offers in particular a computer program product, comprising program code which, when loaded and executed by a computer system, causes it to carry out a method for determining movement parameters for at least one eye of a user in one of the described embodiments.

However, the determination according to the invention of a radius of movement of the at least one marked point of the eye is not limited to the analysis of the gaze deflection in a single direction or in a single plane. A method preferably includes determining a first radius of movement and a second radius of movement for gaze deflections in two different planes, preferably perpendicular to one another. Preferably, analogous to the first and second image data, third and fourth image data of at least a partial area of the eye are generated by means of the image recording device in a third and fourth viewing direction. The third and fourth line of sight can be determined by analogous measures to the first and second line of sight, ie they can be defined or determined. The third and fourth viewing directions are particularly preferably defined or determined in such a way that they lie essentially parallel to a plane to which the first and second viewing directions are not parallel at the same time. Thus, a first eye movement between the first and the second line of sight is not parallel to a second eye movement between the third and the fourth line of sight. The first and the second viewing direction are particularly preferably essentially parallel to a plane which is perpendicular to a further plane to which the third and fourth viewing direction are parallel. In this case, the first and second viewing direction are preferably essentially parallel to a common horizontal or vertical plane, while the third and fourth viewing direction are correspondingly preferred as parallel to a common vertical or horizontal plane. While the first viewing direction differs from the second viewing direction and the third viewing direction differs from the fourth viewing direction, the third or the fourth viewing direction can certainly correspond to the first or the second viewing direction. Thus, two different eye movements can also be evaluated on the basis of only three different viewing directions. This is very efficient in particular when the first or second viewing direction, which coincides with the third or fourth viewing direction, is determined as the zero viewing direction, in particular is predetermined.

A data output device of a device according to a preferred embodiment of the invention is preferably designed to output the radius of movement, in particular the first and/or second radius of movement. In particular, it is not necessary to directly output the position of the corresponding center of rotation of the eye and/or the position of the corresponding axis of rotation.

• 1A und 1B: schematische Darstellungen zur Veranschaulichung einer Rotationsbewegung eines Auges;
• 2: eine schematische Darstellung zur Veranschaulichung beispielhaft erfasster Messgrößen zur Ermittlung von Rotationsparametern in einer bevorzugten Ausführungsform der Erfindung;
• 3A und 3B: schematische Darstellungen zur Veranschaulichung von Sehaufgaben gemäß einer bevorzugten Ausführungsform der Erfindung mit Hilfe von Fixationstargets;
• 4A und 4B: schematische Darstellungen zur Veranschaulichung von Sehaufgaben mit Hilfe von Fixationsobjekten an der Vorrichtung gemäß einer bevorzugten Ausführungsform der Erfindung;
• 5: eine schematische Darstellung eines Auges und des Zustandekommens verschiedener Reflexe an Grenzflächen des Auges;
• 6A und 6B: schematische Darstellungen zur Veranschaulichung des Zustandekommens des ersten und vierten Purkinje-Reflexes; und
• 7A und 7B: schematische Darstellungen zur Veranschaulichung des Zustandekommens des dritten Purkinje-Reflexes.

The invention is described below by way of example with reference to the accompanying drawings of preferred embodiments. It shows:

• 1A and 1B 1: schematic representations to illustrate a rotational movement of an eye;
• 2 FIG. 1: a schematic representation to illustrate measured variables recorded by way of example for determining rotation parameters in a preferred embodiment of the invention; FIG.
• 3A and 3B 1: schematic representations to illustrate visual tasks according to a preferred embodiment of the invention with the aid of fixation targets;
• 4A and 4B 1: schematic representations to illustrate visual tasks with the aid of fixation objects on the device according to a preferred embodiment of the invention;
• 5 : a schematic representation of an eye and the occurrence of various reflexes at the interfaces of the eye;
• 6A and 6B : schematic representations to illustrate the formation of the first and fourth Purkinje reflex; and
• 7A and 7B : Schematic representations to illustrate the formation of the third Purkinje reflex.

A few preferred examples for determining movement parameters, in particular rotation parameters of a user's eye, are described below, which can in particular be integrated into an aberrometer or use elements of an aberrometer.

According to a first preferred embodiment, a camera is used to measure the position of the pupil. This example can also be applied in an analogous manner to the evaluation of the position of the iris, in particular based on the detection of the outer edge of the iris. In order to determine the rotation parameters, in particular a radius of movement of a marked point of the eye with a camera, the angle of the deflection of the eye and the associated change in the position of the marked point (e.g. center of the pupil or corneal vertex) must be known. These are determined in the method described in this section with an image recording direction or preferably specified by a fixation object or target.

The detection of pupils in video images can take place in a known manner.

The same applies to the detection of the iris, even if this is not repeatedly pointed out in the following. Since the calculation of the rotation magnitudes is based on the relationship between translation and rotation, the subject is not allowed to move his head. The head and chin rest are preferably designed in such a way that visual tasks can be carried out without moving the head and this is securely fixed. If necessary, a bite bar can also be used.

In 1A and 1B the movement of a pupil 102 when the eye is deflected by the angle α is sketched. The projections d′ of the pupil diameter and the projection a′ of the position of the center of the pupil can be measured using a camera as the image recording device. A telecentric system is preferably used for this purpose, since these quantities can be measured independently of the distance of the eye from the camera system, which simplifies the calibration. However, autofocus systems or systems in which the distance is measured or can be ignored are also possible.

The respective viewing direction (hereinafter angle α) is particularly preferably specified by the visual task. This is preferably done using a fixation target (see Fig 3A and 3B) , since the direction is given directly and even those with severe ametropia can easily fulfill this visual task. Alternatively, Fixationsob projects (see 4A and 4B) possible, even if the accuracy of fixation targets is often better, especially for people with severe ametropia.

A fixation target represents in particular a light source which is designed to emit a light field at least partially in the direction of the user's eye to be detected in such a way that all light rays within the light field run essentially parallel to a common fixation plane. In this case, the task is to look into the at least partially directed field of light, thereby aligning the eye along the axis (or plane) of the field. The direction of the field with respect to the recording device or recording direction is known or specified.

To align the eye in a plane, a light field is used, the light of which runs parallel in the plane in which the eye is to be deflected and has the direction in which the eye is to be deflected. On the other hand, the light field perpendicular to this is diffuse, which means that the subject's line of sight is not specified in this plane. If the gaze is only deflected horizontally in this way, the subject can adopt his habitual head and body posture.

However, the viewing direction can also be completely specified if the light field runs not only parallel to a plane, but completely parallel to an axis or direction. As a result, the subject can no longer freely choose his viewing direction in this plane either if he wants to follow the light field with his eyes. The rotational position of the eye is thus completely defined by the light field in both angular coordinates.

Above all, the radius of the pupil movement can be determined particularly safely and reliably in this way, since the precise viewing direction is only specified by the light field and is therefore independent of the exact position of the eye in front of the fixation target. Furthermore, the line or the point can still be perceived as a line or point (albeit possibly broadened or blurred) even by people with defective vision and can be fixed if necessary.

The light field for aligning the view in a plane can be generated, for example, by inserting a narrow, rectangular, diffusely luminous surface into the focal plane of a cylindrical lens in such a way that its orientation runs parallel to the cylinder axis of the lens. A light field generated by a spherical lens and a small - preferably circular - luminous surface in the focal plane is used to completely align the view in space. The width of the field or the diameter of the circle determine how much the actual direction of individual "rays" deviate from the target direction.

3A and 3B illustrate various visual tasks using fixation targets. The subject, whose head 302 is shown schematically, fulfills in 3A a first visual task in that the at least one eye 304 is guided in a first viewing direction by a light field generated by a first fixation target 306. In a second visual task according to 3B the at least one eye 304 of the test person is guided in a second viewing direction by the light field generated by a second fixation target 308.

According to a further preferred embodiment already mentioned, at least one fixation object is used for the visual tasks. In this case, the task is to fix a point or a line whose position is known at least to the extent that it can be specified relative to a recording coordinate system and thus also relative to the head. The position of the fixation object relative to the recording coordinate system can either be defined in a system data storage device or can be determined from the image data generated by the image recording devices.

The fixation object (in particular as a marking or light source, e.g. in the form of a point or a line) can be designed as any sufficiently small marking that scatters or emits light sufficiently diffusely, at least in the direction of the subject (e.g. colored marking or LED). The fixation object can also be designed to be switchable. This is particularly advantageous if at least partially different fixation objects are to be used for different visual tasks. These can additionally or alternatively differ in design (e.g. color) in order to enable a simple description of the visual task.

4A and 4B illustrate various visual tasks using fixation objects. The subject, whose head 402 is shown schematically, fulfills in 4A a first visual task by looking at a first fixation object 406 with at least one eye 404 in a first viewing direction. In a second visual task according to 4B he looks at a second fixation object 408 with the at least one eye 404 in a second viewing direction.

The visual task preferably consists of looking once in the direction of the camera axis, whereby a first viewing direction (α ₁ =α ₀ =0) is defined, which can correspond in particular to the zero viewing direction, and once with the deflection by the angle α ₂ = Δα ₁₂ according to a second viewing direction different from the first viewing direction. In this case it follows from the drawing in 1A for the radius r of movement of the center of the pupil, the relation $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)}$$

In this case, Δa′ ₁₂ =a′ ₂ −a′ ₁ designates the change in the projection a′ of the position of the pupil center (or the projection of the change in the position of the pupil center) between the first and second viewing directions. If an aberrometer camera is used, it is preferably perpendicular to the plane of the face. However, the camera used to measure the rotation parameter can also be positioned laterally (preferably at an angle of about 25° to the normal of the face planes). This allows the angular deflection between the two visual tasks to be increased. While the test person has to look straight ahead and sideways in the first arrangement, here he can look deflected in one direction and in the other. This doubles the angle of the gaze deflection to around 50°, which increases accuracy.

Due to the sinusoidal dependency, the accuracy of the angle measurement decreases for large angles. Furthermore, a solution without an oblique camera is simpler, since the mostly central camera of the aberrometer can be used. For two recordings with the deflection of the line of sight by the angles α ₁ and α ₂ from the camera axis, the following applies when using signed quantities and using Δa' ₁₂ =a' ₂ -a' ₁ $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)-\text{sin}\left(a_1\right)}$$

In this case, a′ ₀ , ie the projection of the position of the pupil 102 (or the center of the pupil) when looking in the direction of the camera axis, does not have to be known. This case is in 1B demonstrated. Since, in said preferred embodiment, the camera is particularly preferably perpendicular to the plane of the face, it is preferably deflected in both directions—preferably symmetrically. In this case, an angle (and if a' ₀ = 0 also a measured deflection) is negative, so that the amounts add up. For the symmetrical case (α ₂ =-α ₁ =α) it follows: $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{2}\cdot \text{sin}\left(a\right)}$$

vorzugsweise an die n gemessenen bzw. vorgegeben Werte a'_i bzw. a_i angepasst.More preferably, the position of the pupil 102 (in particular the center of the pupil) is measured for more than two deflections. In this case, the free parameters (radius r and position a′ ₀ of the pupil (or pupil center) when deflected parallel to the camera axis) of the corresponding system of equations $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\text{sin}\left(a_i\right)}\forall i=1...n$$

preferably adapted to the n measured or predetermined values a' _i or a _i .

If no additional fixation target or object is to be used, the deflection can also be determined from the distortion of the pupil 102 .

Assuming that the pupil 102 is a disc, the following applies to the projection d' _i of the pupil diameter d in the plane of the camera axis when the viewing direction is deflected by the angle α _i : $$\begin{array}{l}\mathrm{i.e}{\text{'}}_i=\mathrm{i.e}\cdot \text{cos}\left(a_i\right)\\ a_i={\text{cos}}^{-1}\left(\frac{\mathrm{i.e}{\text{'}}_i}{\mathrm{i.e}}\right)\end{array}$$

berechnet werden.If the diameter d of the pupil 102 remains constant between two recordings, one of which (α ₁ =α ₀ =0, a' ₁ =a' ₀ and d' ₁ =d' ₀ =d) with a viewing direction in the direction of the camera axis and one (α ₂ =α, a' ₂ and d' ₂ ) with the unknown deflection α ₂ =Δα ₁₂ =α, the radius r can be calculated according to the sketch 1A and using Δa' ₁₂ =a' ₂ -a' ₁ to $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a\right)}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left({\text{cos}}^{-1}\left(\frac{\mathrm{i.e}{\text{'}}_2}{\mathrm{i.e}}\right)\right)}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2}{\mathrm{i.e}{\text{'}}_1}\right)}^2}}$$

be calculated.

If one allows changes in the pupil size between the recordings, it makes sense to measure not only the diameter d of the pupil 102 in the direction of the deflection but also the diameter h of the pupil 102 perpendicular thereto. If the pupil widens uniformly, then for the recording configuration described above (a recording with a deflection of the viewing direction in the direction of the camera axis, ie α ₁ =0, a' ₁ =a' ₀ , d' ₁ =d' ₀ =d ₀ and h ' ₁ = h' ₀ = h ₀ , and a recording with unknown Deflection α ₂ =α, a' ₂ , d' ₂ and h' ₂ = h ₂ ) according to the schematic representation in 2 : $$\begin{array}{l}\frac{\mathrm{i.e}{\text{'}}_2}{{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="DE102011009260B4\_0047.png"\; state="\{\{state\}\}">H</figure-callout>}}_2}=\frac{\mathrm{i.e}{\text{'}}_0\cdot \text{cos}\left(a\right)}{H_0}\\ a={\text{cos}}^{-1}\left(\frac{\mathrm{i.e}{\text{'}}_2\cdot {\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="DE102011009260B4\_0047.png"\; state="\{\{state\}\}">H</figure-callout>}}_0}{\mathrm{i.e}{\text{'}}_0\cdot H_2}\right)\end{array}$$

With this, the radius is calculated $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a\right)}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left({\text{cos}}^{-1}\left(\frac{\mathrm{i.e}{\text{'}}_2\cdot {\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="DE102011009260B4\_0047.png,DE102011009260B4\_0051.png"\; state="\{\{state\}\}">H</figure-callout>}}_1}{\mathrm{i.e}{\text{'}}_1\cdot H_2}\right)\right)}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2\cdot {\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="DE102011009260B4\_0047.png,DE102011009260B4\_0051.png"\; state="\{\{state\}\}">H</figure-callout>}}_1}{\mathrm{i.e}{\text{'}}_1\cdot H_2}\right)}^2}}$$

Assuming that the pupil 102 is circular, the recording with the line of sight parallel to the camera axis can be omitted and replaced by one in which the line of sight is also deflected. In both recordings, the diameter is measured parallel and perpendicular to the deflection plane. The following then applies to the angles of the deflections $$\mathrm{i.e}{\text{'}}_i=H{\text{'}}_i\cdot \text{cos}\left(a_i\right)\left(\text{With}i=\mathrm{1,}\mathrm{2,}...\right)$$

wird vorzugsweise auch eine etwaige Änderung der Pupillengröße zwischen den beiden Aufnahmen berücksichtigt. Das Vorzeichen muss dabei je nach Sehaufgabe gewählt werden. Für zwei Auslenkungen der Blickrichtung in unterschiedliche Richtungen von der Kameraachse müssen die Beträge der Wurzel addiert werden, für zwei Auslenkungen in die gleiche Richtung von der Kameraachse subtrahiert.When calculating the radius after $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2}{H_2}\right)}^2}\pm \sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_1}{H_1}\right)}^2}}$$

any change in the pupil size between the two recordings is preferably also taken into account. The sign must be selected depending on the visual task. For two deflections of the line of sight in different directions from the camera axis, the amounts of the square root must be added, for two deflections in the same direction from the camera axis they must be subtracted.

To improve the statistical measurement uncertainty, recordings can also be made and evaluated for several deflections. This is particularly useful with this method, since no fixation targets or objects are necessary. In a preferred embodiment, a video sequence is recorded while the subject moves his eye from one direction to the other. The individual images of this sequence can be evaluated afterwards or in situ. With an additional evaluation, images classified as bad can be excluded from the evaluation.

angepasst werden können.Preferably, only the position of the pupil (in particular the center of the pupil) and its diameter in the direction of the plane of eye deflection are measured in n recordings. In this case, the radius r and the position a' ₀ of the pupil when deflected parallel to the camera axis and the diameter d of the pupil are the free parameters that are attached to the measured values a' _i and d' _i for the system of equations $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_i}{\mathrm{i.e}}\right)}^2}}\forall i=1...n$$

can be adjusted.

If possible changes in the pupil size are to be taken into account during the recording of the sequence, the diameter is preferably also measured perpendicularly to the plane of the gaze movement. For a circular pupil, the free parameter of the pupil diameter does not apply, and the following system of equations is preferably used as the system of equations for the adjustment: $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_i}{H{\text{'}}_i}\right)}^2}}\forall i=1...n$$

Particularly preferably, the ratio between the pupil diameter perpendicular to the plane of gaze deflection (h) and parallel to it (d) is introduced as a free parameter µ=h/d to be adjusted: $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\sqrt{1-{\left(\mu \cdot \frac{\mathrm{i.e}{\text{'}}_i}{H{\text{'}}_i}\right)}^2}}$$

In this way, the condition of a circular pupil can preferably be resolved and an elliptical shape with constant ellipticity can be assumed instead.

In further preferred embodiments, other distinctive features of the eye are measured in addition to or instead of the center of the pupil. All of the above statements with reference to the attached schematic representations of preferred embodiments can be understood analogously with another distinguished point of the eye instead of the center of the pupil expressly described. Examples of this are the iris, its outer edge and its center of gravity or center. Other relevant variables include the subject's individual angles between said axes (e.g. optical axis of the eye, optical axis of the schematic eye, visual axis, fixation line, pupillary axis, in particular according to the definition in DIN 5340) and generalized eyes pivot points (points of intersection of individual axes for different gaze deflections).

Furthermore, in preferred embodiments of the invention, the radius of movement can be individually measured for different directions of displacement (e.g. horizontal, vertical or in the direction of the muscles of the eye movement). The data obtained in this way can then also be used to determine the subject-specific parameters of more complex models, such as different pivot points in space for different pivot axes and their relative position to one another, as well as pivot point ellipsoids. Furthermore, the rolling of the eye can be measured, for example, using the pattern of the iris as a function of the deflection of the eyes.

The variables to be determined can be determined as a function of external influences on the eye. The convergence (distance of the fixed object, preferably "infinity" and "40 cm") and the brightness (photopic, mesopic and scotopic) are of particular relevance. The former can be implemented via images with corresponding virtual distances or correspondingly distant fixation objects, which can each also be adjustable. To measure the quantities at different brightnesses, the device can include lighting devices that generate a corresponding brightness. The following limits preferably apply to the brightness ranges (variable and individually different): scotopic: 3×10 ^-6 cd/m ² (perception threshold) to approximately between 0.003 and 0.03 cd/m ² ; mesopic: between about 0.003 and 0.03 cd/m ² to about between 3 and 30 cd/m ² ; photopic: from something between 3 and 30 cd/m ² .

When using optics that do not allow telecentric approximations within the measurement volume, the formulas must be supplemented with appropriate calibration functions, which can also include a measured distance from the camera system, or the variables specified in the formulas must be understood as correspondingly calibrated variables . If the distance is measured, it can also be used directly to calculate the angles and radii.

The elements (camera and fixation devices) are preferably arranged in such a way that the right and left eye can be measured equally. However, the elements can also (at least in part) be present twice and the individual elements can be used for the corresponding eye.

With the help of intrinsic or extrinsic marks fixed to the head, which can be chosen or selected automatically, semi-automatically or manually, head movements between the individual recordings can be tracked and the positions, angles and lengths measured in the respective recordings can be corrected accordingly.

In the following, such a method is presented as an example for a telecentric projection: The lateral offset in the camera plane and a rotation of the head around the camera axis are particularly relevant and easy to detect. This is done by simply tracking the position of these marks in the image. Rotation of the head about axes perpendicular to the camera axis can be detected by tracking the length of distances between individual marks or the dimensions of extended marks. Angle changes or angular deflections can be calculated from the shortening or lengthening in the projection into the camera plane. Naturally, this tracking is particularly accurate if the configuration or extension of the marks has individual components in at least three spatial directions that do not lie in one plane. A component is understood to mean the connection between two marks or an edge of an extended mark. Only a translation along the camera axis cannot be determined due to the telecentricity of the lens, which - in this configuration - has no influence on the measurement.

• - vorzugsweise die zur Pupillometrie genutzte - verwendet. Es kann jedoch auch eine dezidierte Kamera zum Einsatz kommen.

One of the cameras of the aberrometer is preferably used as the image recording device

• - preferably used for pupillometry - used. However, a dedicated camera can also be used.

In methods in which fixation targets or objects are used, the advantage of this invention is that at least one of the fixation targets or objects can be used, which is also used to adjust the deflection and accommodation of the eye in the abberometric or pupillometric measurements will. This applies in particular to visual tasks in which the line of sight should be set parallel to the camera axis. However, one or more dedicated fixation targets or objects can also be used additionally or exclusively.

Aberrometers can be designed as closed systems (the subject looks directly at the fixation device) or open-field systems (the subject has an almost unobstructed view, the measuring beam path is realized by beam splitters or similar). This allows visual tasks to be set in the room.

Since the calculation of the rotation quantities is based on the relationship between translation and rotation, it is preferable if the subject does not move his head. Accordingly, the head and chin rest are preferably designed in such a way that visual tasks can be carried out without moving the head and this is securely fixed. If necessary, a bite bar can also be used.

Furthermore, recordings that are necessary in the context of abberometry or pupillometry can also be used to measure the rotation parameters. This applies in particular to recordings in the viewing direction parallel to the camera axis. As a result, fewer recordings are required overall to measure the optical and mechanical properties, which makes the measurement process faster and easier and more comfortable for both the test person and the examiner.

The information about the size and shape of the pupil obtained in the course of measuring the rotation variables can be used as the results of pupillometry, which is useful in connection with aberrometry. This also applies to different convergences and brightnesses. Conversely, the measurement method according to the invention can also access an existing pupillometric unit.

In a further preferred embodiment, the determination of the movement parameters and in particular the movement radius of a marked point of the eye is based on an analysis of the Purkinje reflexes of the eye. In this case, Purkinje reflections are preferably used in a known manner to determine the viewing directions. The method described here uses the information contained in the reflections to determine the rotation parameters. For the fixation of the head, what has already been stated above preferably applies in an analogous manner, as does the preferred integration into an aberrometer system.

The Purkinje reflections are the most important reflections of a light source that occur in the front of the eye. The Purkinje reflexes I and II (first and second Purkinje reflex) arise at the front and rear boundary surface of the cornea, the reflexes III and IV (third and fourth Purkinje reflex) at the corresponding surfaces of the lens.

5 shows a schematic image of the eye and the formation of these reflections at the individual boundary layers. In 6A one can see that the front surface of the cornea C and the back surface of the lens L form a clam shell combination to a good approximation. This means that the two surfaces have the same radius of curvature and the center of curvature is in the center of the other surface. Due to this geometry, said surfaces depict infinitely distant objects as a virtual (Reflex I) or real image (Reflex IV) in the plane in which the two spherical mirrors intersect. This is approximately the pupil plane. The beam path is in 6B shown. The two images are superimposed for infinitely distant objects lying on the optical axis (see Fig 6A) . With an increasing angle of incidence of the rays to be imaged (measured to the perpendicular to the pupil plane), the reflections within the pupil plane migrate apart (compare 6B) . The emergence of reflex III on the front surface of the lens is in 7 illustrated.

Preferably, those described in TN Comsweet and HD Crane, "Accurate two-dimensional eye tracker using first and fourth Purkinje images", J. Opt. Soc. At the. 63 (8), 921-928 (1973) described details about the names and properties of the Purkinje reflections with reference to 5 until 7 applied accordingly in connection with the inventive use of the Purkinje reflexes. In particular, a rotation of the eye relative to a light source leads to a change in the angle of incidence and thus to a change in the distance between the images of reflexes I and IV. A translational movement of the eye, on the other hand, leads to a joint movement of these two reflexes, since the angle of incidence changes in this case does not change. By analyzing these two reflexes and separating the movement of the common center of gravity from the relative movement of the two reflexes, the translation and rotation of the eye can be measured independently of one another.

Since the intensity of the fourth reflection is only about 1% of the intensity of the first, very intense illumination is preferred. In order not to blind the subject unnecessarily, illumination with infrared light is preferably used to generate the reflected images.

At least two acquisitions (image data) are made of at least reflections I and IV at different deflections. In the context of the invention, “detection” means a determination of the position of the reflections by selection in the recording of an image recording device, in particular by methods based on movable mirrors and quadrant diodes or by other suitable methods.

The lateral position or change in position of the cornea-lens system and the angular deflections or changes in deflection are determined from the detected reflections. Position changes and/or angular deflections are particularly preferably determined from the first and/or fourth Purkinje reflex according to one of the methods detailed above.

The rotation parameters (in particular the radius of the rotation movement, i.e. the movement radius of the at least one marked point of the eye) are derived from the changes in position and angle or angular deflections, preferably analogously to the methods already described above and adapted to the respective geometry. The determination of the change in position and angle or angular deflection and the determination of the movement radius can take place in a common algorithmic step without the exact position and deflection of the eye being specified or output as an “intermediate result”. Such a procedure offers particular advantages in the case of special calibration methods.

In the following sections some possibilities are listed as examples. The symbols introduced above are used.

der Radius der Bewegung berechnet werden.The reflexes I and IV are preferably measured for two deflections of the eye with an unknown viewing direction. In a second step, the change in the lateral position of the cornea-lens complex between the two images and the viewing angles are determined from this data using Purkinje transformations. In this regard, reference is made in particular to the statements above. From this, according to the formula $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)-\text{sin}\left(a_1\right)}$$

the radius of movement can be calculated.

The position and direction of the eye can also be measured for more than two deflections. This can advantageously be done using a continuous visual task (e.g. looking from left to right) and video recording, in which all individual images or a suitable subset are evaluated.

anzupassen. Sollten auf Grund der Art der Kalibrierung nur relative Winkel ${\alpha }_i^{rel}$

gemessen werden können, wird vorzugsweise der Winkeloffset α₀ als zusätzlicher Parameter angepasst: $$r=\frac{a{\text{'}}_i-a{\text{'}}_0}{\text{sin}\left({\alpha }_i^{rel}+{\alpha }_0\right)}\forall i=1\dots n$$

In this case - as already explained above - the free parameters (radius r and position a' ₀ of the pupil when deflected parallel to the camera axis) of the corresponding system of equations are related to the n measured values a' _i or a _i , $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\text{sin}\left(a_i\right)}\forall i=1...n$$

to adjust. Due to the nature of the calibration, only relative angles should be used $a_i^{\mathrm{right}el}$

can be measured, the angular offset α ₀ is preferably adjusted as an additional parameter: $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\text{sin}\left(a_i^{\mathrm{right}el}+a_0\right)}\forall i=1...n$$

wobei der Winkeloffset bekannt - vorzugsweise Null - sein oder aus der Anpassung hervorgehen kann. Bei entsprechender Auslegung oder Kalibrierung kann in allen Fällen auch der Längenoffset a'₀ bekannt sein und muss dann nicht mit angepasst werden.If, in addition, the angles are only known up to one factor, this factor m (a kind of Hirschberg quotient) can also be adjusted because of the non-linearity of the sine wave - given a sufficient number of measurements with sufficiently large deflections. The system of equations then becomes: $$\mathrm{right}=\frac{a{\text{'}}_i-a{\text{'}}_0}{\text{sin}\left(m\cdot a_i^{\mathrm{right}el}+a_0\right)}\forall i=1...n$$

where the angular offset can be known - preferably zero - or can be derived from the fitting. With a corresponding design or calibration, the length offset a' ₀ can also be known in all cases and then does not have to be adjusted.

This step can also be summarized with the Purkinje transformation. In the general case one gets a system of equations of the form $$\mathrm{right}=ƒ\left({\overline{p}}_i,\overline{k},\overline{l}\right)\forall i=1...n$$

The vectors p̅ _i contain the measured positions of the reflections of the measurements 1...n, k̅ the constant parameters (e.g. from calibration measurements, geometric conditions of the structure or standard parameters of the eye) and/the parameters to be adjusted in addition to r (compare above).

In order to increase the accuracy, it is preferable to determine parameters of the Purkinje transformation by measuring with a known deflection in order to calibrate the system. The known deflection is preferably achieved by using a fixation object or—preferably—a fixation target.

In this case the angle of the corresponding measurement is known and not determined according to step 2, so that: $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)-\text{sin}\left(a_1\right)}$$

In a particularly preferred embodiment, the visual axis of the target or the fixation object corresponds to the axis of the Purkinje structure. In this case, when determining α ₁ =0, the formula simplifies to: $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)}$$

The position and direction of the eye can also be measured for more than two deflections. This can advantageously be done using a continuous visual task (eg looking from left to right) and video recording, in which all individual images or a suitable subset are evaluated. The results of the calibration measurement with known deflection are used to determine the parameters of the Purkinje transformation. In the case of a recording with a known alignment of the eye, these are advantageously the angular offset α ₀ and the offset a′ ₀ of the lateral position. In this case, preferably—as already described—the free parameters of the corresponding system of equations are adapted to the n measured values a′ _i or α _i . Depending on the calibration, in addition to the radius r, these can include the position a' ₀ of the pupil when deflected parallel to the camera axis, the factor m and the offset α ₀ . Here, too, the evaluation is preferably combined with the Purkinje transformation.

bzw. $$r=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left({\alpha }_2\right)}$$

bzw. $$r=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{2}\cdot \text{sin}\left({\alpha }_2\right)}$$

A further increase in accuracy can be achieved if two viewing directions are specified in a suitable manner and the measured positions of the Purkinje reflections are used to calibrate the system. Cases are preferred in which one fixation target or one fixation object coincides with the axis of the Purkinje structure (case 1) or two are arranged symmetrically to it (case 2). If only the two recordings used for calibration are used, the angles of the visual task can be used directly. It is therefore not necessary to carry out a dedicated calibration, only the lateral deflections are calculated from the reflection images. Again, the above formulas apply to the general case as well as the preferred cases mentioned: $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)-\text{sin}\left(a_1\right)}\left(\text{general}\right)$$

or. $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(a_2\right)}$$

or. $$\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{2}\cdot \text{sin}\left(a_2\right)}$$

Here, too, the position and direction of the eye can be measured in the manner already described above for more than two deflections and, as described there, evaluated by adapting the corresponding free parameters of an equation system. The offset of the angular position α ₀ (see above) and the lateral offset a′ ₀ and also the generalized Hirschberg quotients or the factor m are preferably determined from the two recordings of the calibration measurements.

If only the recordings used for calibration are used, the angles of the visual task can be used directly and no dedicated calibration needs to be carried out. Preferably, only the lateral deflections are calculated from the reflected images, from which the radius can be determined by adapting the system of equations.

In principle, standard parameters can be used to calibrate the viewing direction measurement. The respective sizes of the eye according to Gullstrand are given as examples. Variables such as Hirschberg quotients are relevant for relative calibration and angles such as alpha, kappa or gamma (definitions according to DIN 5340) are relevant for absolute calibration.

The accuracy and reliability of the measurement of the direction of gaze can be increased if quantities that describe the movement of the reflexes as a function of the deflection are determined individually as parameters for the respective test person. This can be done as part of a calibration measurement, the adjustment of several measurements or a correspondingly combined approach. Some calibration methods with at least one dedicated measurement are described below.

A relative calibration is understood to mean the dependency of the change in the position of the Purkinje reflexes on the change in the deflection of the eyes, without the position of the reflexes being known in a particular position (eg zero viewing direction). The relationship between this translational deflection of the first Purkinje reflex and the angular deflection is referred to in the literature as the Hirschberg quotient. Based on this definition, the nth Hirschberg quotient stands for the corresponding relation for the nth Purkinje reflex. In the case of evaluation methods based on the measurement of the reflections I and IV, the Hirschberg quotients I and IV or only a part of them determined. For this purpose, the angle of an eye rotation can be specified by appropriate visual tasks (using fixation objects or—preferably—fixation targets) and the change in the position of the reflexes can be measured. Analogously to the Hirschberg quotients of the individual reflexes, the corresponding ratio for the center of gravity or relative movement of two reflexes can also be determined. This can be relevant especially for non-linear Purkinje transformations. These non-linearities in the movement of the reflections can be taken into account by determining the corresponding quotients as a function of the angle or additional quotients of a higher order (ie pre-factors for terms of a higher order in a series expansion).

Absolute calibration: To calculate the radius from the angular deflection, it is not enough just to know the change in angle. Rather, due to the non-linearity of the sine, the angle of the eye deflection to the normal to the projection surface must be known. This knowledge is called absolute calibration. In the simplest case, a recording at at least one predetermined angle is sufficient. The necessary parameters can then be derived from the position of at least one Purkinje reflex. The defined deflection of the eye required for this is achieved by a fixation object or a fixation target. Preferred procedures are the deflection of the eye parallel to said axis in at least one recording and two deflections lying symmetrically to this axis in at least two recordings.

In many cases it is advantageous to determine both the position of the reflections and the position of the pupil from image processing. In this way, the angle of the deflection can be determined not only from the relative movement of reflexes I and IV to one another, but also from the distance of the first reflex from the center of the pupil. In this case—in contrast to the procedure described so far—there is no need to record and evaluate the position of reflex IV.

Furthermore, the (lateral) position of the pupil can be determined purely from the position of the center of the pupil in the camera image (see Section 1) and the angular deflection using at least two pieces of information (from the position of reflex I, position of reflex IV, pupil diameter, position of the pupil center).

Additional information about the geometry of the anterior segment of the eye can be obtained from the position of reflexes II and III. Of course, this information can also be used to determine the orientation of the eye. Reflex III is particularly interesting in this context, as it occurs on the front of the lens. As a result, more advanced models can be used when determining the deflection and corresponding additional variables can be determined.

• - bei definierter Auslenkung durch ein Target oder ein Objekt - die Lage der entsprechenden Achse des Auges handeln. Aus vorbereitenden Messungen oder Annahmen über den Aufbau des Auges und der Aparatur sind die Parameter bekannt.

In general terms, to determine the variables of interest, n individual measurements i=1...n are carried out, with the parameters being recorded in each case. These can be, for example, the position of reflexes, the pupils and

• - with a defined deflection by a target or an object - act on the position of the corresponding axis of the eye. The parameters are known from preparatory measurements or assumptions about the structure of the eye and the apparatus.

„gelöst“ werden. Je nach Struktur der Funktion und der Anzahl der Messungen kann das Gleichungssystem eindeutig lösbar oder überbestimmt sein. In letztem Fall kann eine beste Lösung durch Anpassung (z.B. Minimierung der quadratischen Fehler mit einer geeigneten Abstandsfunktion) gefunden werden.There is also a sentence l , from parameters resulting from the measurements. The quantities of interest are summarized in the vector r̅. The relationships are described by the function f. Finally, the system of equations must $$\overline{\mathrm{right}}=ƒ\left({\overline{p}}_i,\overline{k},\overline{l}\right)\forall i=1...n$$

be "solved". Depending on the structure of the function and the number of measurements, the system of equations can be uniquely solvable or overdetermined. In the latter case, a best solution can be found by fitting (eg minimizing the squared errors with a suitable distance function).

In the case of the calibration methods described above - also in the case of absolute calibration - the focus is on the "absolute" deflection of the eye in relation to the recording system of the reflexes. A statement is not necessarily made about the absolute position of the different axes of the eye in space and their relative position in the eye to one another. However, these can also be determined to derive other relevant variables.

Other relevant variables include the subject's individual angles between said axes (e.g. optical axis of the eye, optical axis of the schematic eye, visual axis, fixation line, pupillary axis, definition according to DIN 5340) and generalized eye rotation points (intersection points of individual said axes for different gaze deflections).

The method preferably includes a determination of the rotational quantities for movements in different planes. In particular, the variables to be determined (eg the radius of rotation around a defined pivot point) can be measured for different directions of the deflections (eg horizontal, vertical or in the direction of the muscles of the eye movement). The data obtained in this way can then also be used to determine the subject-specific parameters of more complex models, such as different pivot points in space for different pivot axes and their relative position to one another, as well as pivot point lipoids. Furthermore, the rolling of the eye is preferably measured, for example using the pattern of the iris as a function of the deflection of the eyes.

Diffuse point light sources and pinhole camera optics are usually used to generate and record the reflections. The algorithms known from the literature are also based on this. However, configurations can also be used in which work is carried out with telecentric optics or directed illumination (extended fields of light with a predetermined direction, preferably parallel light). When determining the position of the eye from the laws of reflection and refraction, it must be taken into account that in such configurations instead of fixed points (punctiform, diffuse light source or aperture point of the pinhole camera), fixed directions (extended, directed light field or direction of the detected radiation) can kick.

When using optics that do not allow telecentric approximations within the measurement volume, the formulas must be supplemented with appropriate calibration functions, which can also include a measured distance from the camera system. If the distance is measured, it can also be used directly to calculate the angles and radii.

Other distinctive features of the eye can also be measured in addition to or instead of the center of the pupil. Examples of this are the iris, its outer edge and its center of gravity or center.

The variables to be determined can be determined as a function of external influences on the eye. Of particular relevance are the convergence (distance of the fixed object, preferably "infinity" and "40cm") and the brightness (photopic, mesopic and scotopic). The former can be implemented via images with corresponding virtual distances or correspondingly distant fixation objects, which can each also be adjustable.

Claims (15)

Method for determining movement parameters for at least one eye of a user with the following steps: - Generating first image data of at least a partial area of the eye in a first viewing direction of the eye; - Generating second image data of at least a partial area of the eye in a second viewing direction of the eye that differs from the first viewing direction, the first and second image data being generated with an image recording device which is fixed relative to the user's head in order to generate the first and second image data that it assumes the same position relative to the user's head for generating the first and second image data, - determining a change in position of at least one marked point of the eye; and - Determining a radius of movement of the at least one marked point of the eye from the determined change in position and as a function of the first and second viewing directions. procedure after claim 1 , wherein the generation of the first and second image data takes place by means of a telecentric image recording device. Method according to one of the preceding claims, wherein the at least one distinguished point comprises a center of the pupil and/or a center of the iris and/or the corneal vertex of the eye. Method according to one of the preceding claims, which includes specifying the first and second viewing direction by means of a fixation target, which is designed to emit a light field at least partially in the direction of the user's eye to be recorded by means of the image recording device in such a way that all light rays within the light field essentially parallel to a common plane of fixation, wherein the light field is emitted during the generation of the first image data with a first plane of fixation and during the generation of the second image data with a second plane of fixation that differs from the first. Method according to one of the preceding claims, which includes specifying the first and second line of sight by means of a fixation object which is designed to output an optical signal suitable for guiding or fixing the line of sight of the user in at least one specified fixation position. A method according to any one of the preceding claims, which comprises: - a determination of a first primary, projected diameter of the pupil and/or the iris of the eye in a primary direction from the first image data; and - determining a second primary, projected diameter of the pupil and/or iris of the eye in the primary direction from the second image data, the radius of movement of the at least one marked point of the eye being determined from the determined change in position and at least the ratio of the first and second primary, projected diameter is determined. procedure after claim 6 , wherein the generation of the first image data takes place in a first viewing direction of the eye, which is parallel to an optical axis of the image recording device, wherein a position change Δa' ₁₂ of a center point of the pupil and/or a center point of the iris is recorded as a change in position of the at least one marked point and where the radius of movement r of the center of the pupil or the center of the iris according to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2}{\mathrm{i.e}{\text{'}}_1}\right)}^2}},$

with the first primary projected diameter d' ₁ and the second primary projected diameter d' ₂ is determined. procedure after claim 6 or 7 , which comprises: - a determination of a first secondary, projected diameter h ₁ of the pupil or the iris of the eye in a secondary direction perpendicular to the primary direction from the first image data; and - determining a second, secondary, projected diameter h ₂ of the pupil or iris of the eye in the secondary direction from the second image data, the radius of movement of the at least one marked point of the eye being determined from the determined change in position and the conditions $\frac{\mathrm{i.e}{\text{'}}_1}{H_1}$

and $\frac{\mathrm{i.e}{\text{'}}_2}{H_2}$

of the respective primary d\ or d' ₂ to the secondary h ₁ or h ₂ , projected diameter is determined. procedure after claim 8 , wherein the generation of the first image data takes place in a first viewing direction of the eye, which is parallel to an optical axis of the image recording device, wherein a position change Δa' ₁₂ of the center of the pupil or of the center of the iris is detected as a change in position of the at least one marked point , and where the movement radius r of the center of the pupil or the center of the iris according to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2\cdot H_1}{\mathrm{i.e}{\text{'}}_1\cdot H_2}\right)}^2}},$

is determined. procedure after claim 8 , wherein a change in position Δa' ₁₂ of the center of the pupil or the center of the iris is detected as the change in position of the at least one marked point, and wherein the radius of movement r corresponds to the center of the pupil or the center of the iris $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_2}{H_2}\right)}^2}\pm \sqrt{1-{\left(\frac{\mathrm{i.e}{\text{'}}_1}{H_1}\right)}^2}},$

is determined. Method according to one of the preceding claims, which comprises illuminating the eye with a reference light source, wherein the acquisition of the first image data comprises acquiring a first position of the first Purkinje reflex of the eye and a first position of the fourth Purkinje reflex of the eye, and that Capturing the second image data includes capturing a second position of the first Purkinje reflex of the eye and a second position of the fourth Purkinje reflex of the eye, and wherein the change in position of the at least one marked point of the eye and preferably a change in angle between the first and second viewing direction of the eye can be determined as a function of the first and second positions of the first and fourth Purkinje reflex. procedure after claim 11 , wherein the generation of the first image data takes place in a first viewing direction of the eye, which is parallel to an optical axis of the image recording device, wherein a position change Δa' ₁₂ of a center point of the pupil and/or a center point of the iris is recorded as a change in position of the at least one marked point is, wherein the method also includes determining a change in position Δp ⁽¹⁾ of the first Purkinje reflex, and wherein the radius of movement r of the center of the pupil or the center of the iris according to $\mathrm{right}=\frac{\mathrm{\Delta }a{\text{'}}_{12}}{\text{sin}\left(H^{\left(1\right)}\cdot \mathrm{\Delta }{p}^{\left(1\right)}\right)},$

is determined with a predetermined value h ⁽¹⁾ . Device for determining movement parameters for at least one eye of a user, comprising: - an image data recording device, which is designed to generate first image data at least a partial area of the eye in a first viewing direction of the eye and for generating second image data of at least a partial area of the eye in a second viewing direction of the eye, wherein the image data recording device can be fixed relative to the user's head in such a way that it is used to generate the first and second image data occupies the same position relative to the user's head; and - an evaluation device which is designed for - determining a change in position of at least one marked point of the eye; and -- determining a movement radius of the at least one marked point of the eye from the determined change in position and as a function of the first and second viewing directions. device after Claim 13 , comprising at least one fixation target, which is designed to at least partially define the first and/or second viewing direction by emitting a light field in that all light rays of the light field run essentially parallel to a common fixation plane. A computer program product comprising computer-readable instructions which, when loaded into a memory of a computer and executed by the computer, cause the computer to perform a method according to any one of Claims 1 until 12 performs.

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